Plasma processing unit

ABSTRACT

A plasma processing unit includes: a processing chamber ( 10 ); a first electrode ( 5 ) and a second electrode ( 11 ) which are placed in the processing chamber ( 10 ) and arranged to face each other; and a quartz plate ( 13 ) arranged on one of the surfaces of the first electrode ( 5 ) facing the second electrode ( 11 ) to protect the first electrode ( 5 ), the plasma processing unit being configured to excite reaction gas in the processing chamber ( 11 ) to generate plasma between the first electrode ( 5 ) and the second electrode ( 11 ) so that a target object placed on one of the surfaces of the second electrode ( 11 ) facing the first electrode ( 5 ) is subjected to plasma processing, wherein one of the surfaces of the quartz plate ( 13 ) facing the second electrode ( 11 ) is rough-finished.

This application is a Continuation of International Application No. PCT/JP2005/010674, filed on Jun. 10, 2005.

TECHNICAL FIELD

The present invention relates to a plasma processing unit.

BACKGROUND ART

In the process of manufacturing electronic devices such as liquid crystal display devices and semiconductor devices, dry etching techniques have been widely used as a method for forming fine patterns.

The dry etching techniques are required to achieve high aspect ratio, high etch rate, high selectivity and high uniformity. It is also required to prevent the occurrence of particles (fine-grained contaminants).

The aspect ratio is the ratio of width to depth of a trace formed on a substrate by etching. The selectivity is the ratio between etch rate of a material to be etched and that of an etch mask material and an underlayer material.

For example, if etching is carried out with low uniformity, the traces obtained by etching may suffer overetch (excessive etching) and underetch (insufficient etching) due to the difference in etch rate. This may possibly exert a significant effect on the subsequent manufacturing process.

Further, if a plurality of traces extending parallel to each other are formed by etching and the particles described above remain therebetween, a short may occur to reduce the manufacturing yield of the products.

Now, a dry etching unit is known as one of the plasma processing units. The dry etching unit is configured to excite reaction gas introduced into a processing chamber by high frequency or microwave to obtain plasma, i.e., to provide atoms and molecules (reaction seeds) of high chemical activity. In the dry etching unit, dry etching is carried out by reacting the reaction seeds generated by the plasma with an etching target material and discharging the reaction product in the form of volatile gas out of the chamber through a vacuum pumping system.

In recent years, a unit provided with a plasma source capable of generating high density plasma in a high vacuum condition has been commonly used. In many cases, the plasma source is configured to introduce an electromagnetic wave into the processing chamber from outside through a quartz component.

In the dry etching unit configured to introduce the electromagnetic wave through the quartz component, the reaction product may adhere to the surface of the quartz component and drop therefrom. This may possibly generate particles that contaminate the inside of the processing chamber.

In view of the above, Patent Publication 1 discloses a semiconductor manufacturing device engineered to reduce the possibility of particle generation.

FIG. 4 is a schematic view illustrating the structure of a semiconductor manufacturing device 130 disclosed by Patent Publication 1.

The semiconductor manufacturing device 130 is a high density plasma etching unit in which an electromagnetic wave generated by a TCP (transformer coupled plasma) electrode 122 is introduced into a processing chamber 110 through a quartz top plate 113 to excite reaction gas supplied therein from a gas supply 124, thereby generating plasma for treating a wafer 112. In the semiconductor manufacturing device 130, the quartz top plate 113 is heated with radiant heat of a far infrared heater 123 placed above the quartz top plate 113.

[Patent Publication 1] Japanese Unexamined Patent Publication No. 2000-164565

DISCLOSURE OF THE INVENTION

Since the conventional semiconductor manufacturing device 130 is configured to heat the quartz top plate 113, it is considered that the reaction product is less likely to adhere thereto. However, the far infrared heater 123 is indispensable as a means of heating the quartz top plate 113.

Further, as the upsizing of glass substrates for liquid crystal display devices has been rapidly proceeding in recent years, it has been demanded to perform etching of the substrate, i.e., plasma processing, with improved uniformity.

In view of the above-described situation, the present invention has been achieved. An object of the present invention is to prevent contaminant particles from occurring in a plasma processing unit and to perform the plasma processing with uniformity.

MEANS OF SOLVING THE PROBLEM

The present invention is directed to a plasma processing unit having a first electrode and a second electrode, wherein one of the surfaces of a protection plate for protecting the first electrode facing the second electrode is rough-finished.

A plasma processing unit according to the present invention includes: a processing chamber; a first electrode and a second electrode which are placed in the processing chamber and arranged to face each other; and a protection plate arranged on one of the surfaces of the first electrode facing the second electrode to protect the first electrode, the plasma processing unit being configured to excite reaction gas in the processing chamber to generate plasma between the first and second electrodes so that a target object placed on one of the surfaces of the second electrode facing the first electrode is subjected to plasma processing, wherein one of the surfaces of the protection plate facing the second electrode is rough-finished.

According to the above-described structure, the protection plate shows high heat absorbency because the one of the surfaces of the protection plate facing the second electrode is rough-finished. Therefore, the protection plate is easily heated and a reaction product generated during the etching of the target object is likely to be volatilized around the protection plate. Therefore, the reaction product is less likely to adhere to the protection plate.

Further, since the one of the surfaces of the protection plate facing the second electrode is rough-finished, the surface area thereof increases. Therefore, the rough-finished surface is able to hold an increased amount of the reaction product even if it adheres thereto. This prevents the occurrence of contaminant particles due to the drop of the reaction product.

Further, since the one of the surfaces of the protection plate facing the second electrode is rough-finished, reaction gas molecules generated by the plasma collide against the rough-finished surface of the protection plate and bounce therefrom at various angles. Therefore, the reaction gas is distributed uniformly in the processing chamber, thereby making uniform plasma processing possible.

For these reasons, the occurrence of the particles is prevented easily and the plasma processing is carried out uniformly.

According to Patent Publication 1, as shown in FIG. 4, one of the surfaces of the quartz top plate 113 facing the far infrared heater 123, i.e., the surface of the quartz top plate 113 facing the TCP electrode 122 corresponding to the first electrode of the plasma processing unit of the present invention, is sandblasted so as to improve the heat absorbency of the quartz top plate 113 and reduce the particles generated. However, according to the plasma processing unit of the present invention, the one of the surfaces of the protection plate facing the second electrode is rough-finished, the generation of the particles is prevented and the plasma processing is carried out uniformly.

The protection plate may be made of quartz or ceramic. By so doing, the first electrode is protected by a quartz or ceramic plate. As the quartz and ceramic plates are highly resistant against plasma, the first electrode is effectively protected by the quartz or ceramic plate.

The first electrode may include a top electrode made of conductive material and a dielectric substance provided between the top electrode and the protection plate.

As the dielectric substance included in the first electrode is protected by the protection plate, the dielectric substance is prevented from deteriorating by the plasma generated during the etching. As a result, the effect of uniform dispersion of an electromagnetic wave by the dielectric substance is maintained.

The one of the surfaces of the protection plate facing the second electrode may be blast-finished. This makes it easy to obtain the rough-finished surface of the protection plate.

The plasma processing may be dry etching. Accordingly, the dry etching is carried out uniformly.

EFFECT OF THE INVENTION

According to the plasma processing unit of the present invention, one of the surfaces of the protection plate for protecting the first electrode facing the second electrode is rough-finished. This improves the heat absorbency of the protection plate, and therefore the reaction product is less likely to adhere to the protection plate. Further, the surface area of the one of the surfaces of the protection plate facing the second electrode is increased so that the protection plate is able to hold an increased amount of the reaction product adhered thereto. Therefore, the occurrence of particles due to the drop of the reaction product is less likely to occur. Moreover, since the reaction gas molecules generated by the plasma bounce from the rough-finished surface at various angles, the plasma processing is carried out uniformly. For these reasons, the occurrence of the particles is prevented easily and the plasma processing is carried out uniformly.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating the structure of a dry etching unit 30 according to an embodiment of the present invention.

FIG. 2 shows a model for the behavior of a molecule to a quartz plate 13 a whose surface is specular.

FIG. 3 shows a model for the behavior of a molecule to a quartz plate 13 b whose surface is rough-finished.

FIG. 4 is a schematic view illustrating the structure of a conventional dry etching unit 130.

EXPLANATION OF REFERENCE NUMERALS

5 First electrode

10 Processing chamber

11 Second electrode

12 Substrate (target object)

13, 13 a, 13 b Quartz plate (protection plate)

14 Dielectric substance

15 Top electrode

25 Plasma

30 Dry etching unit (plasma processing unit)

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention is explained in detail. In the following embodiment, a dry etching unit in an ICP (ion coupled plasma) mode is taken as an example of the plasma processing unit. However, it should be noted that the present invention is not limited to the following embodiment and applicable to other etching modes than the ICP mode. Further, the present invention may be applied to, not only the dry etching units, but also sputtering apparatuses and CVD (chemical vapor deposition) apparatuses in which plasma processing is carried out.

Hereinafter, a dry etching unit 30 according to an embodiment of the present invention is explained with reference to FIG. 1. FIG. 1 is a schematic view illustrating the structure of the dry etching unit 30 of the present invention.

The dry etching unit 30 includes a processing chamber 10, an exhaust system 20 and high frequency power sources 16 and 18.

In the processing chamber 10, a first electrode 5 and a second electrode 11 facing the first electrode 5 are provided.

The first electrode 5 includes a top electrode 15 made of conductive material such as metal and a ceramic dielectric substance 14 formed on one of the surfaces the top electrode 15 facing the second electrode 11.

A quartz plate 13 is placed on one of the surfaces of the first electrode 5 facing the second electrode 11 as a protection plate. The protection plate may be made of ceramic in place of quartz.

One of the surfaces of the quartz plate 13 facing the second electrode 11 is rough-finished by blasting. The surface roughness of the quartz plate 13 may be expressed, for example, as arithmetic average roughness Ra of about 5 μm.

The second electrode 11 is configured such that a substrate 12 to be processed is fixed onto one of the surfaces thereof facing the first electrode 5 by adsorption using an electrostatic chuck or the like.

The first and second electrodes 5 and 11 and the wall of the processing chamber 10 are connected to a cooler such as a water-cooled chiller (not shown) so that their temperatures are controlled.

The first electrode 5 and the high frequency power source 16 are connected via a condenser 17, while the second electrode 11 and the high frequency power source 18 are connected via a condenser 19. Further, the high frequency power sources 16 and 18 and the processing chamber 10 are grounded.

Next, explanation of how to operate the thus-configured dry etching unit 30 is provided.

First, a substrate 12 as a target object is brought into the processing chamber 10 and placed on the second electrode 11.

Then, high frequency power (frequency: 13.56 MHz) is applied to the first electrode 5 from the high frequency power source 16 and high frequency power (frequency: 6.0 MHz) is applied to the second electrode 11 from the high frequency power source 18. Simultaneously, reaction gas is fed into the processing chamber 10 through a gas pipe (not shown), the dielectric substance 14 and the quartz plate 13.

As a result, an electromagnetic wave is introduced into the processing chamber 10 through the quartz plate 13 and the dielectric substance 14 to excite the reaction gas, thereby generating high density plasma 25. Then, chemical reaction occurs between a target material on the substrate 12 and the molecules of the reaction gas having high chemical activity to etch the target material.

During this time, the quartz plate 13 shows high heat absorbency because the one of the surfaces thereof facing the second electrode 11 is rough-finished. Therefore, the quartz plate 13 is easily heated and a reaction product generated during the etching of the target material is likely to be volatilized around the quartz plate 13. Therefore, the reaction product is less likely to adhere to the quartz plate 13.

Further, since the one of the surfaces of the quartz plate 13 facing the second electrode 11 is rough-finished, the surface area thereof increases. Therefore, the rough-finished surface is able to hold an increased amount of the reaction product even if it adheres thereto. This prevents the occurrence of contaminant particles due to the drop of the reaction product.

Further, since the one of the surfaces of the quartz plate 13 facing the second electrode 11 is rough-finished, the molecules of the reaction gas generated by the plasma 25 and having high chemical activity collide against the rough-finished surface of the protection plate and bounce therefrom at different angles.

FIGS. 2 and 3 show models for the behavior of a molecule, respectively. FIG. 2 shows a model for the molecule behavior to a quartz plate 13 a whose surface is not subjected to blasting to keep it specular, while FIG. 3 shows a model for the molecule behavior to a quartz plate 13 b whose surface is subjected to blasting to make it rough.

More specifically, as shown in FIG. 2, a molecule 21 of the reaction gas is reflected on the specular surface of the quartz plate 13 a such that the incident angle and the exit angle agree with each other. In contrast, as shown in FIG. 3, the molecule 21 of the reaction gas collides against the rough-finished surface of the quartz plate 13 b and bounces therefrom at various angles.

With use of the quartz plate 13 b having the rough-finished surface as described above, the molecules of the reaction gas are dispersed. Therefore, the reaction gas is distributed uniformly in the processing chamber 10 and the etching is carried out with improved uniformity.

For these reasons, the occurrence of contaminant particles is prevented easily and the etching is carried out uniformly.

Next, explanation of an actually-performed experiment is provided.

As an example of the invention, a target substrate was dry-etched in the same dry etching unit as that of the above-described embodiment. Then, the surface of the dry-etched substrate was subjected to measurement using a stylus profilemeter (13 spots).

Then, a comparative example to the example of the invention is explained.

Specifically, a target substrate was dry-etched using a dry etching unit including a quartz plate whose surface is not rough-finished. The surface of the dry-etched substrate was then subjected to measurement using the stylus profilemeter (13 spots).

The results are shown below.

According to the example of the invention, the maximum surface height (maximum value) was 20.0 nm and the minimum surface height (minimum value) was 16.4 nm. Therefore, the etching uniformity was 9.8%.

The etching uniformity was calculated by the following equation. Etching uniformity=(maximum value−minimum value)/(maximum value+minimum value)×100

It should be noted that the smaller the value of the etching uniformity is, the higher the etching uniformity is.

According to the comparative example, the maximum surface height (maximum value) was 19.8 nm, while the minimum surface height (minimum value) was 15.2 nm. Therefore, the etching uniformity was 13.2%.

Thus, the example in which the dry etching unit of the invention was used showed etching uniformity of 9.8%, while the comparative example showed 13.2%. Thus, it is confirmed that the present invention improves the etching uniformity.

INDUSTRIAL APPLICABILITY

As described above, the present invention allows uniform plasma processing. Therefore, the present invention is useful for dry etching units. 

1. A plasma processing unit comprising: a processing chamber; a first electrode and a second electrode which are placed in the processing chamber and arranged to face each other; and a protection plate arranged on one of the surfaces of the first electrode facing the second electrode to protect the first electrode, the plasma processing unit being configured to excite reaction gas in the processing chamber to generate plasma between the first and second electrodes so that a target object placed on one of the surfaces of the second electrode facing the first electrode is subjected to plasma processing, wherein one of the surfaces of the protection plate facing the second electrode is rough-finished.
 2. The plasma processing unit of claim 1, wherein the protection plate is made of quartz or ceramic.
 3. The plasma processing unit of claim 1, wherein the first electrode includes a top electrode made of conductive material and a dielectric substance provided between the top electrode and the protection plate.
 4. The plasma processing unit of claim 1, wherein the one of the surfaces of the protection plate facing the second electrode is blast-finished.
 5. The plasma processing unit of claim 1, wherein the plasma processing is dry etching. 